A paramount design consideration for any airline manufacturer is the safety of passengers, the aircraft and crew. In order to further promote this goal, pilots and crew undergo rigorous training before being allowed to fly a given model of aircraft. This training involves practicing routine flight operations as well as rehearsing what to do in the case of numerous emergency situations.
To help pilots remember the steps to be performed for a given aircraft situation, most aircraft are supplied with a quick reference handbook. The handbook contains a plurality of paper checklists that list notes and steps, or "action items," to be performed for such normal flight phases as takeoff, landing, parking, etc., as well as checklists for emergency situations such as cabin decompression, engine fire, hydraulic system failure, etc.
Although such paper checklists have proved satisfactory in the past, they are subject to numerous drawbacks. First, the quick reference handbook may become misplaced in an aircraft cockpit and not be locatable by a crew during an emergency situation. Secondly, the index of a checklist manual may be such that a pilot is unable to quickly locate the appropriate checklist for a given situation. Thirdly, paper checklists are generic and not tailored to the particular configuration of the aircraft being flown. For example, the checklist might tell the pilot to do something to the "affected engine" instead of the "left engine" if there is a problem with the left engine, etc. Finally, the paper checklists provide no means for indicating which steps have already been performed so that a pilot may inadvertently perform the same step twice or omit a step.
To solve the problems associated with paper checklists, electronic checklist systems have been developed. The Boeing Company has developed such an electronic checklist system that is the subject of commonly assigned, co-pending U.S. patent application Ser. No. 07/762,309, filed Sep. 18, 1991 and entitled Electronic Checklist System (hereinafter '309 Application), the specification of which is herein incorporated by reference.
The electronic checklist system described in the '309 application provides an electronic display of the action items and notes listed on the paper checklists provided in the quick reference handbook. In addition, the system indicates the action items that have been completed by the pilot or crew by displaying them in green, while the uncompleted action items that have yet to be performed on a checklist are shown in white. Once the pilot completes the action item or acknowledges the note, the color of the display changes to indicate the step has been completed. For action items that require a pilot to change the setting of a switch, lever, etc., that is monitored by the aircraft's sensing systems, the checklist system monitors the aircraft's data bus systems to verify that a pilot has completed a particular step. Such action items are referred to as closed-loop. The system also provides for open-loop action items, whereby a sensor cannot be interrogated to see if the action item is performed. To complete an open-loop action item, a pilot manually indicates that the action item has been completed by selecting a "done" key on a user interface. While such an electronic checklist system is an improvement over prior art paper checklist systems, the electronic checklist system described in the '309 application is not designed to provide a single, integrated checklist for multiple situations, such as multiple aircraft faults.
While it is extremely rare in aircraft operation that more than a single fault is detected at exactly the same time, this can occur. For example, a first fault may be detected, such as an engine fire, and shortly thereafter another fault, such as loss of hydraulic pressure, will be detected. For a flight crew that is equipped with a paper checklist system, assuming the faults occur sufficiently far apart in time, a dual fault situation would be dealt with by opening the quick reference handbook to the checklist that deals with engine fires and completing the action items in the order listed. Upon completion of the first checklist, the crew would then turn to the checklist associated with the second fault, i.e., the loss of hydraulic pressure and complete the action items listed. The problem with this approach is that often a crew may not be able to finish the first checklist before a second fault is detected. The crew then has to keep the quick reference handbook open to both checklists and reason what action items are to be performed and in what order. Given the number of faults that are possible in a complex machine such as an aircraft, it is not possible to provide a single paper checklist tailored to every possible combination of faults. Such a quick reference handbook would be too large to be carried by the crew and it would take too long for the crew to find the appropriate checklist.
As indicated above, the '309 electronic checklist system works well for displaying the action items and notes of a checklist produced for a single fault. However, it does not have the capability of combining two or more checklists in the case of multiple fault detection. The problem with combining checklists is that the order in which the action items are to be performed often depends upon the current flying condition of the aircraft, its phase of flight (i.e., takeoff, cruise or landing), altitude, air temperature, etc. Thus, in order to combine two checklists, the electronic checklist system must be able to determine the current flying condition of the aircraft and know how the flying condition affects the priority of the action items so that the action items on the checklist can be merged and prioritized in the correct order. In addition, any redundant or conflicting action items that occur because the action items for multiple faults were combined must be eliminated so as not to confuse the pilot.